Evaporative emission control systems are widely used in internal combustion engine powered motor vehicles to prevent evaporative fuel, i.e., fuel vapor, from being emitted from the fuel tank into the atmosphere. There are generally three main components that control such evaporative emission operations: vapor control/rollover valves, vapor management valves and fuel carbon canister(s). One or more of the above components may typically be found in an internal combustion engine powered motor vehicle to control evaporative emission.
In the event that one or more of the above evaporative emission control components malfunction, fuel vapors may be vented improperly resulting in reduced engine performance and possible release of vapors into the atmosphere. It is thus desirable to employ an on-board diagnostic system capable of detecting malfunctions and leaks in the evaporative purge system so that corrective measures may be taken.
Various techniques for monitoring the evaporative purge system are known. For example, see U.S. Pat. Nos. 5,261,379, 5,263,462, 5,275,144, 5,295,472, 5,299,545, 5,333,589, 5,333,590, 5,353,771, 5,355,863, and 5,363,828. However, the known prior art fails to disclose a method and system for monitoring the evaporative purge system in a significantly reduced amount of time and in a way in which false failure indications are eliminated.